Originally Posted by Portolan

Restaurants have to be members of Dining Plus for you to get credit. No tie, specifically, to UAL Visa as any registered credit card will work with D+. I don't recal now whether it was an opt-in entry in my D+ profile, but I get an email for every qualifying meal that also summarizes the points and bonus earned.

Of course, every now and then you'll happen to eat in a D+ restaurant that you didn't know was a member and you'll get some unexpected mileage.